A computer management system attains, through one line, the uniform and steady system management through an agent such as monitoring of fault and power control in a computer connected by LAN as well as a public line, and system management for an off-state of the computer or abnormal operation state of the computer such as remote power control and notice and diagnosis of critical fault by the direct connection with a service processor through the line. The system includes an agent connected to a computer to be managed for executing instructions on the computer to be managed, a service processor board having a processor independent from the computer to be managed for monitoring fault in the computer to be managed and controlling power of the computer to be managed, a manager for executing instructions on a management computer and conducting controls such as fault monitoring and power control through the agent over a network including a public line, and a service processor manager directly connected to the service processor for conducting remote power-on and receiving and diagnosing critical fault. The service processor and the service processor manager are provided with switching circuits for switching an asynchronous interface for remotely connecting to the computer to be managed and an asynchronous interface for directly connecting to a local processor of the service processor.